The present invention relates generally to magnifying a digital image and more particularly to magnifying a digital image using an edge map.
The proliferation of digital imagery cries for better ways to magnify an image. In a traditional magnification process, additional pixels are added into the original pixels. Then the size of the image is magnified so that the distance between adjacent pixels is maintained to be the same as that in the original digital image.
Different methods are available to add the additional pixels. One method simply replicates pixels--adds a number of pixels surrounding every existing pixel to form a block of pixels with the same level. FIG. 1 shows an image before magnification and FIG. 2 shows the image after magnification by such a method. Observe the small square blocks of unpleasant pixels about 0.5 mm wide making up the image, and the jagged edges, such as the edges of the petals of the flowers.
Another method generates the additional pixels by interpolating the levels of adjacent original pixels. FIG. 3 shows a magnified image formed by such a bilinear-interpolation method. This method substantially removes the blocks of unpleasant pixels and the jagged edges. However, the crisp edges in the original image are blurred due to the averaging effect.
It should be apparent from the foregoing that there is still a need for a method to magnify a digital image that maintains its crisp edges.